1. Field of the Invention
The present invention relates to a plasma display apparatus, and more particularly, to a plasma display apparatus including a heat radiation sheet that both prevents visible residual images from forming while allowing for easy attachment and detachment of the heat radiation sheet to and from a plasma display panel (PDP).
2. Description of the Related Art
In general, a plasma display apparatus is an apparatus for displaying an image through a gas discharging phenomenon, and can replace a cathode ray tube (CRT) device due to excellent display features such as display capacity, brightness, contrast, residual image, and viewing angle. In the plasma display apparatus, a gas filled between electrodes is discharged by direct current (DC) voltage or alternating current (AC) voltage applied to the electrodes, and accordingly, ultraviolet rays are radiated to excite a phosphor and emit visible light.
A plasma display panel (PDP) included in the plasma display apparatus can be classified into an AC type and a DC type according to a discharging mechanism. In the DC type plasma display panel, electrodes included in the plasma display panel are directly exposed to a discharge gas filled in a discharging cell, and the voltage applied to the electrodes is directly applied to the discharge gas. In the AC type plasma display panel, since the electrodes are separated from the discharge gas by a dielectric layer, charged particles generated in a discharging operation are not absorbed by the electrodes, a wall charge is formed, and the discharging operation occurs using the wall charge. Therefore, since the plasma display apparatus uses the discharging operation for displaying images, the plasma display panel generates a lot of heat.
The plasma display panel is mounted in an external case with a circuit device. The panel is coupled to a chassis base, and the chassis base is coupled to the external case. The chassis base is manufactured using a thermal conductive metal substance so that the heat of the panel can be drawn out from the panel. A heat radiation sheet is disposed between the chassis base and the panel in order to promote the radiation of heat toward the chassis base.
The heat radiation sheet used to remove the heat generated on the plasma display panel can be manufactured using various materials, and includes a thermal conductive filler such as copper powder, graphite powder, and aluminum powder.
However, the conventional heat-radiation sheet has a low thermal conductive coefficient of about 1 W/m·K, thus decreasing a heat radiating function. When heat is not effectively drawn away from the plasma display panel, the brightness of the PDP is lowered in the discharging cell, where much heat accumulates. Accordingly, this causes a difference between the brightnesses of a cell that emits light and a cell that does not emit light, and an entire brightness of the plasma display panel is lowered. Moreover, when the discharging strength increases in order to improve the brightness of the plasma display apparatus, more heat is generated from the plasma display panel, thus aggravating the above problem.
Therefore, a highly thermal conductive heat radiation sheet that is manufactured using highly oriented graphite is used recently in order to improve the heat conductive function. However, the coupling forces between particles in the highly thermal-conductive sheet are weak and the highly thermal-conductive sheet is less flexible, thus generating dust and being brittle and thus prone to fracturing in a bending process. Moreover, when the heat radiation sheet is separated from the plasma display panel to repair the panel, some of the heat radiation sheet adhered to the display panel surface may not be removed, thus requiring additional manual work.
As the plasma display apparatus becomes larger, it is more difficult to handle the heat radiation sheet. That is, the heat radiation sheet is formed to be thin, for example, with a thickness of 1 mm through 2 mm, thus when the thin heat radiation sheet is adhered to the plasma display panel of larger area, it is difficult to handle the heat radiation sheet. In addition, after adhering the heat radiation sheet to the plasma display panel, an air gap may be generated between the plasma display panel and the heat radiation sheet. When the heat radiation sheet is fabricated using the graphite for high heat conductivity, the above problems become more severe. Therefore, what is needed is a heat radiation sheet structure that is both effective in drawing heat away from the display while being easy to attach and detach from the display.